Discharge electrode structure for electrical precipitation apparatus



Nov. 14, 1944. F. w. PHILLIPS 2,362,716

DISCHARGE ELECTRODE STRUCTURE FOR ELECTRICAL PRECIPITATION APPARATUSFiled Nov. 21, 1942 2 Sheets-Sheet 1 0 g 7 .1. 20 17 15 v v 22 L/..,.\n.,..m i w 25 ATTORNEY:

Nov. 14, 1944. F. w. PHILLIPS DISCHARGE ELECTRODE STRUCTURE FORELECTRICAL PRECIPITATICN APPARATUS 2 Sheets-Sheet 2 Filed NOV, 21, 1942iksosQ/cz MPH/Lugs,

INVENTQR.

' ATTORNEY.

Patented Nov. 14, 1944 DISCHARGE ELECTRODE STRUCTURE FOR ELECTRICALPRECIPITATION APPARATUS Frederick W. Phillips, Toronto, Ontario, Canada,assignor to Western Precipitation Corporation, Los Angeles, Calif., acorporation of California Application November 21, 1942, Serial No.466,467

11' Claims.

This invention relates generally to apparatus for electricalprecipitation of suspended particles from gases, and more particularlyto discharge electrode structures for such electrical precipitationapparatus.

It is common practice in electrical precipitation apparatus to employ adischarge electrode structure including one or more discharge electrodesin the form of linearly-extended elements of relatively small diameter,or having formations of relatively small radius of curvature, wellknownexamples including wires, small diameter rods, twisted ribbons andtwisted square bars. This discharge electrode structure, which inoperation is maintained at a high uni-directional potential, is soconstructed and mounted that the discharge electrode elements extend inparallel spaced relation with respect to an opposing grounded electrodestructure which is of nondischarging character, such as anextendedsurface plate, relatively large diameter pipes, or the like, andthe particle-laden gas is passed between the opposing electrodes, as iswell understood in the art.

In the following description and appended claims, the term dischargeelectrode will be understood to designate an electrode that facilitatescorona discharge therefrom, because it has a configuration thatestablishes a sufiiciently high potential gradient at or near itssurface to create corona discharge before there is a disruptivedischarge or sparkover. For this purpose, the discharge electrodeusually takes the form ofa member of small surface area, such as a smalldiameter wire or a rod provided with sharp edges or points, wherebythere may be created in the immediate vicinity thereof a sufficientlyhigh electric field intensity to cause ionization and corona discharge.The term non-discharging electrode will be understood to designate anelectrode that minimizes or prevents corona discharge therefrom becauseit has a configuration that establishes a sufiiciently low fieldconcentration at or near the surface to suppress corona discharge atelevated potentials lower than the voltage required for disruptivedischarge or sparkover. For this purpose, a non-discharging electrode isusually one of extended surface area, substantially free from sharpcorners or other parts of sharp surface curvature at all portionswhichare located within the electric field, so as substantially to avoidionization or corona discharge at that electrode.

The discharge electrode structure for precipitators of the classmentioned usually embodies 5 'tential supporting means for the element.

supporting means which supports each linearlythe positions as to berestrained against longitudinal movement and in good electrical contactwith the supporting means, and the elements beingmerely confined by thesupporting means against transverse movement at the other position orpositions and being left free for longitudinal movement to accommodate'longitudinalexpansion and contraction relative to the supporting means.The support provided at the last-mentioned position orv positions is notsuch as affords a good electrical connection between the element and thesupporting means. H

When the precipitator is handling certain types of gases, as, forexample, dry converter gases, there issome considerable unavoidablesparking and arcing between thehigh potential discharge electrodestructure and the grounded non-dischargingelectrode structure. Thissparking or arcing may occur between any point on any of the linearlyextending discharge electrode elements and a point on the opposinggrounded electrode structure. Consequently, any tendency thereof tocauseburning away of the discharge electrode elements is not apt tocause serious trouble because such sparks or arcs do not usually occurrepeatedly at any one point on a discharge electrode element. However,when such a spark or an arc jumps the gap between the groundednon-discharging electrode structure and a point on a discharge electrodeelement, the potential of such point on the discharge electrode elementis very greatly lowered, and a heavy current fiows momentarily betweensuch point and the high posuch point happens to be near the position ofsupport for the element at which the element is longitudinallyrestrained, at which position a good electrical connection between theelement andthe supporting means has been provided, the heavy currentfiow spoken of passes through said electrical connection to thesupporting means without event. But if the-point of-sparkover or archappens to benear a position of supportfor the element at which'onlytransverse restraint has been provided, andat which good electricalconnection is diflicult to provide, arcing will occur between theelectrode element and the supporting means at such position, due to therelatively high potential difierence thus created momentarily betweenthese parts that'; are normally at substantially the same potential.Such arcing between ience, shut-down time for replacement, and

expense.

The primary object of the present invention is,

accordingly, the provision of a discharge e1ec'- trode structure adaptedto be maintained at high potential with respect to an opposing groundedelectrode structure, and embodying linearly-extended electrodeelementssupported at two or more points by supporting means formingparts of said discharge electrode structure and normally maintained atsubstantially the same potential as the electrode elements, in whichsimple and .effective provision is made ,to safeguard against burningofi the extended electrode ele-- ments at their pointsof supporton thesupporting means as a result of arcing therebetween in the mannerdescribed.

Broadly stated, the present invention accomplishes- .this object by theprovision of a hightension discharge electrode structure including asupporting means and linearly-extended dis.- charge electrode elementsmounted thereon, in which the linearly-extended. discharge electrodeelements are each provided with a support at one point on saidsupportingmeans which is'of such character as to provide a. goodelectrical connection between the elementand the supporting means, andwith a positioning member of insulating material mounted on thesupporting means which loosely engages the electrode element at aposition spaced longitudinally from the first-mentioned point of.support and limits transverse movement of the element but leaves, itfree of longitudinal restraint. Such insulation positioning membersprevent arcing at all positions of support for the extended dischargeelectrode elements at which they are provided, causing all current flowsbetween the electrode element and the supporting means totake place atthe points of support at which the electrical con.- nections areprovided, and hence eliminate burnofi of the electrode elements at thosepositions.

The invention will be more fully understood by now referring to thefollowing detaileddescription of several illustrative embodimentsthereof, reference for this purpose being directed to the accompanyingdrawings, in which:

Fig. 1 is an elevation of a high-tension discharge electrode structureembodying the invention; Fig. 2 is an enlarged detail taken from Fig. 1,with parts broken away, showing in detail the nature of the uppersupporting means for the discharging electrode elements; Fig, 3 is avertical medial section showing in detail the nature of the intermediateand lower positioning means for the discharge electrode elements of thestructure of Fig. 1; Fig. 4 is a plan view of the positioning meansshown in Fig. 3; Fig. 5 is a view similarto Fig. 3, but showing amodification; Fig. 6 is another view similar to Fig. 3, but showing afurther modification; Fig, 7 is a somewhat diagrammatic sectiona1 viewof a multiple'gas tube type of precipitator in which the improvements ofthe present invention have been incorporated; Fig. 7a is a detailshowing an insulator of Fig. 7 in enlarged longitudinal section Fig; 8is a fragmentary elevation of a modified form of high-tension dischargeelectrode structure embodying the improvements of the present invention;Fig. 9 is a fragmentary elevation of another type of dischargingelectrode structure embodying the invention; Fig. 10 is a detail sectiontaken on line I 0 l0 of Fig. 9; and Fig. 11 is a detail section taken online I |l I of Fig, 10.

, lshows the high-tension, discharge electrode structure of a typicalelectrical precipitator. The remainder of the precipitator may be of anyconventional or appropriate type; for a description of a completeprecipitator of a type utilizing a discharging electrode structure ofthe type of Fig. 1, see Patent No. 1,846,169, granted February 23, 1932,to C. H. Weiskopf in which an entire discharge electrode structure ofgenerally similar construction is shown as maintained at high potentialwith respect to an opposing grounded electrode structure. Referring nowmore particularly to Fig, 1, the discharge electrode structure,generally designated by numeral I 5, in-

cludes a suitable supporting means or framework embodyinghorizontally-spaced vertical frame bars It, and horizontal,vertically-spaced upper. intermediate and lower cross-members. ll, t8:and I 9, respectively, inter-connecting vertical bars [6. Thesecross-members H, [8, and H2, which are preferably and illustratively inthe form of pipes, m y e provided with any suitable form of m0unt ingson the vertical frame bars is. For instance, intermediate and lowerpipes 18; and I9, may be received in sockets, [8a mounted on bars [6,and upper pipe I! may be supported'at each end by a pin Ila extendingupwardly from the upper flange of a horizontal channel member l'lbmounted on the adjacent frame, bar I6, the pin Ila entering a hole l'lcin the lower side. oi the pipe and supporting the pipe by engaging its,up: per side from below, as clearly il-lustra-tedin Fig; 2.

Horizontal pipes I1, I18 and .19 are provided with horizontally-spacedsets, of vert ically-. aligned openings adapted for reception of thevertical, horizontally-spaced discharging electrode elements 20. Thesedischar ing electrode elements 20 may take various forms.-such as Wires,fine rods, twisted square bars,,twisted ribbons, orother forms oflinearly-extended elements of relatively small diameter or affordingformations of relatively small radius of curvae ture. For the purpose ofthe present disclosure, I show the elements .20 in the form of twistedsquare bars, as illustrated in. Fig. 3. These bars are received invertically-aligned apertures 2| formed in the upper and lower sides ofupper supporting pipe I11, the apertures 2i being preferably of suchsize asv to freely receive .the electrode element but to. confine itcomparatively closely against transverse displacement. The upperendportion of eachelectrode element 20- is preferaby formed with asuitable head which engages the top side of pipe l1, and by which theelement is suspended. In the form. illustrated in Figs. 1 and 2, thishead is formed by the-simple expedient of doubling back the upper endportion 22 of the bar, so that the end. 23 engages the top side of. pipeI! in the manner clearly. illustrated in Fig. 2, This engagement betweenthehead formed on the upper end of bar 20 and at the top side of '15members l8 .and I9, are in electrical contact with bernl'l :and verticalframe members H and are normally maintained at substantially the samepotential. l a

The openings 25 formed in supporting pipes l8 and I9 for passage ofelectrode bars 20 are of substantially increased diameter as comparedwith the openings 2! in the upper pipe I1, and receive insulationpositioning members for the bars 20, preferably and here shown asinsulator bushings or sleeves 26, of glass, ceramic, or anysuitableinsulation material, and preferably formed at their upper ends withshoulder means engageable with the supporting pipe to resistlongitudinal displacement.

In the specific form illustrated in Fig. 3, this shoulder means isprovided by flaring the upper end portion of the bushing outwardly, asindicated at 28. If the bushing is composed of glass, this may easily beaccomplished by heating the upper end portion of the bushing and flaringit while it is hot. The flared portion 28 then serves as the shoulder,and supports the bushing as indicated in Fig. 3. The internal bore 29 ofthe bushing is, of such diameter as will freely or loosely receive thetwisted bar 20, or other linearly-extended electrode element, so as toconfine the bar against transverse displacement, without restraining itlongitudinally. Preferably, the bore in the bushing is of at leastslightly larger diameter than the maximum thickness dimension of theelectrode element, so as to avoid any possibility of frictional bindbetween said element and the bushing. The bushing extends well above andbelow the pipe is to prevent sp-arkover between the electrode elementand the pipe.

Fig. 5 shows a modified insulator bushing 26a, formed at the top with anenlarged head 30 presenting a downwardly-facing annular shoulder 3|which is engageable with the top of pipe l8. As a further modification,the bore 29a of the bushing of, Fig. 5'is shown to diverge in a downwarddirection from a point preferably a short distance below its upper end,as illustrated. This downwardly diverging bore permits foreign objectsthat might become-lodged between the electrode bar 20 and the bushingtowork free and fall from'the bushing somewhat more readily than wouldotherwise be the case. However, this form of bushing may, if desired, bemade with a cylindrical bore. In either case, bushings of this form maybemade by a moulding or other forming operation, using either ceramic orvitreous insulating materials.

Fig. 6 shows an insulator bushing 26b formed at the top with an enlargedhead affording a downwardly-facing annular shoulder 35, the bushing inthis instance being received within discharging electrode elements 20and the. opposed non-discharging electrode (not illustrated) allcurrentflow between the elements 20 and the high-tension supportingstructure I5 is confined to the pointsof'engagement between the heads ofthe elements and the supporting pipe 11, at which the elements 20 havegood electrical connections with the framework IS. The bushings thusserve as longitudinal guides for the extended electrode elements 20,confining them against transverse displacement while permittinglongitudinal movement owing to longitudinal expan sion orcontraction,and at the same time prevent destructive arc-over between the saidelectrode elements and the supporting members l8 and is throughwhichthey are extended.

Figs. 7 and 7a show, the application of the invention to a multiple-tubetype of precipitator employing one or more linearly-extendeddischargeelectl'ode elements in the form of .flexible wires. In Fig. 7,which is largely diagrammatic, numeral 4|] designates generally afragmentarilyindicated gas supply header, understood to be supplied Withgas by way of any suitable inlet means, not shown; numeral 4| designatesa plurality of vertical gas tubes leading upwardly and receiving gasfrom header 4!! and constituting collecting electrodes; and numeral 42designates a fragmentarily indicated gas discharge header into which thegas rising in tubes 4! is discharged. Mounted within header 42, oninsulators indicated at 43, is a horizontal support 44.

for the high-tension discharge electrode elements which extenddownwardly co-axially through collecting electrode tubes 4|. Thesehigh-tension discharge electrode elements, as here shown, in-

clude a pair of relatively heavy hanger elements 1 supportsaid pipewithin header to through nuts and supported by a metal sleeve 36, whichis in turn received by the openings 25 of the pipe. As shown, theupper.end of the sleeve has an outwardly-extending annular flange 37engaging and supporting (bushing shoulder 35, and the underside of saidflange provides a shoulder supported by the pipe. This sleeve 36, thelower end of which terminates substantially short of the lower end ofthe bushing, so as to prevent sparking between the electrode bar and thesleeve, afiords added support and protection for the bushing.

The described insulator bushings placed between the dischargingelectrode elements 20 and the supporting pipes l8 and I9 preventarc-over between said elements and supporting pipes, and, i??? er e epeke 9 r in w en t 19 screwed on their lower ends. Flexible electrodewires t6, hung from pipe 44 in any suitable manner, extend downwardlyfrom the lower ends of tubes 4| through insulator bushings 52 mounted inpipe 38 (Fig. 7a), the insulator bushings 52 being, for example, of thesame type as the bushing 26 of Fig. 3, though they may besomewhatsmaller in diameter. Electrode wires 46 are held taut by meansof weights 53 at their lower ends. As will be evident, the insulatorbushings 52 confine electrode wires 46 against transversedisplacementwithout interfering with relative longitudinal movement between thewiresand the bushings, while at the same time the bushings serve to preventarc-over between the wires and the pipe 48.

Fig. 8 shows a modified form of high-tension discharge electrodestructure, which is in general respects of the same type as that shownin Fig. 1, with the exception that the linearly-extended dischargeelectrode elements are secured at their and understood to comprise oneor morevertical frame'bars 6|", andinter -connecting.upper, interj-'mediate. and lowerv supporting. members 62;. 53 and 64*, respectively,preferably and here' indi-- cated. in the form of pipes; The:linearly-ex:-

tended discharge electrode elements. 6-5;.which. are in this instance ofsufi'icient-stiffness to be supported from their lower ends; may againbe.

typically in the formof twisted square bars, like the bars 20 of Figs. 1and'3. of: the bars have heads 66 which engage the under side of pipe.64, and nuts 6"! threaded onto the bars near the heads 66: are'setagainstthe. top side of the pipe64 to secure the bars against. pass;through and are guided by insulator bushings 68 set into pipes 62 and63, the bushings.G8I'and-" longitudinal displacement. The barsthe-manner of their mounting beingillustratively'the'same as is shown inFig. 3.

Figs. 9 through 11 show another application ofthe invention, thelinearly-extended discharge electrode elements in this instance beinghorizontally disposed. The high-tension supporting frame 'lfl includes avertical central frame member- H of channel section, having flanges I2and outside vertical frame members 13, typically in the form of pipes,which are joined with member H by means of connecting members 14% Thelinearly-extended electrode elements 15 -are again illustratively in theform of twisted square bars,

and will be understood topass horizontally through suitable openings inthe flanges 12 of member H and in the vertical supporting pipes 13-; theends of the bars having heads 16 engageable with the flanges 12', andnuts I1 screw threaded on the bars and set up against said flangescooperating withheads lfi' to support the bars'against longitudinaldisplacement; as well as providing the necessary electrical connectionbetween the bars and the central frame member H. The outer end portionsof bars 15 pass -freely through insulator bushings 18 supported inrelatively large openings 80' in vertical members 13; In the particularexample shown in the drawings, the bushings 18' have flared end portions83 at each end, and the openings 80" are pref erably of such diameter aswill just'receive theseflared end'portions as the bushings are inserted.The bushings being-inserted, their smaller diameter central portions 84,which are of lengths substantially equal to the diameter of the pipes13, rest at the-bottoms of openings 80, and the flared end portions ofthe bushings then serve to restrain the bushings against longitudinaldisplacement withrespect to the pipes'l3;

In summary, in all of the disclosed forms'of the invention, eachlinearly-extended discharge electrode element is provided with a supporton" the discharge electrode supporting frame which confines it againstlongitudinal displace"- ment and which also provides a good electricalconnection between the element and the frame,

and with at least one insulation support'or guide on' said frame whichconfines it against trans verse displacement without restricting itsfree longitudinal movement. This insulationsupport or guide preventscurrentfiow between the'electrode element andithe'fram'eexcept' at thepoint of'support where'the' element is longitudinally restrained;atwhich point a'sufiiciently good e'lec trica-l connection-isprovided'to prevent destructive arcing; and *thus'elimina-tes theburning off of the electrode elements at'their'longitudinallyunrestrainedpoints of support;

It"wi-ll--be' understood' thatthedrawings anddescription are merelyillustrative of and not The lower ends assay-12c:

restrictive on: the invention; and that" various. changes: in: design;.structure: and: arrangement may-be made: without departing from thespirit and scope of the invention or of the appended claims.

1; In: at discharge electrode structure for an electrical precipitator,the combination compris ing: memberelectrode an positioning memberformed of insulating material; and electrically connected conductiveframe members including a member supporting said electrode member' atone-position" and electrically connected thereto and a member supportingsaid positioning mem'- her in loose engagement with said electrodemember at a position" longitudinally removed from said one position'insuch amanner as to'limit" transverse movement of said electrode memberand permit "longitudinal movement thereof relative to said positioningmember.

.connected thereto anda member supporting said positioningmember inengagement with said electrode member at a position longitudinallyremovedlfrom said one position, said positioning member electricallyinsulating said electrode memberfrom said last named supporting-mem--her.

4.- In a discharge electrode structure". for an electrical precipitator,the combination: set: forth inc1aim-3, said positioning member beingformed as a sleeve surrounding said electrode member;

5.-In a discharge electrodevstructure' for an electrical precipitator,the combination as setforth'inclaim 3, said positioning'member beingformed as a sleeve: surrounding said electrode member and projectinglongitudinally at both" ends beyond said last named supportingmeans.

6'- In adischarge. electrode structure-for an" electrical precipitator;the combination as set-1 forthv in claim 3; said last-named supportingmeans comprising a a supporting member extendv ing. transverselywithrespect to said electrode member. and? having an opening through whichsaidaelectrode: member extends, and said positioning 'member beingformed as'a sleeve extend.-

ingthrough said opening; surrounding-saidelec r 1 trode member; andprovided withshoulder'means engaging aid last-mentioned supportingmember to resist'longitudinal movement'of saidsleeve.

'7. In a disc-harge electrode structure for air electrical precipitator,the combination" compris;

ing: a vertically-extending discharge electrode" member; a positioningmember formed'of insulating material loosely engaging said electrodemember in'such manner as to' limit transverse" movement thereof'and'permit longitudinal movement thereof relative to said positioningmem a linearly-extendeddischarge electrode ber; and electricallyconnected conductive frame members including a member supporting said'electrode member at one position and electrically connected thereto anda horizontally-extending supporting member supporting said positioningmember in engagement with said lectrode member at a position verticallyremoved from said one position, said last-named supporting member havingan opening through Which said electrode member extends, and saidpositioning member being formed as a sleeve extending through'saidopening, surrounding said electrode member, and provided with houldermeans engaging said supporting member to support said sleeve thereon.

8. A discharge electrode structure for an electrical precipitatorcomprising a supporting frame formed of electrically conducting materialand including at least two electrically connected frame membersextending substantially parallel to and spaced from each other; alinearly-extended discharge electrode member engaging and supported byand in electrical contact with one of aid frame members; and apositioning member formed of insulating material mounted on andsupported by the other frame member, and loosely engaging said electrodemember in such manner as to limit transverse movement thereof and permitlongitudinalmovement thereof relative to said positioning member, andelectrically insulating said. electrode member from aid other framemember.

9. A discharge electrode structure for an electrical precipitator as setforth in claim 8, wherein the positioning member is formed as a sleevesurrounding the electrode member.

10. In a discharge electrode structure for an electrical precipitator,the combination comprising: a linearly-extended discharge electrodemember; a positioning member formed of insulating material looselyengaging said electrode member in such manner as to limit transversemovement thereof and permit longitudinal movement thereof relative tosaid positioning member; and electrically connected conductive framemembers including a member supporting said electrode member at oneposition against both longitudinal and transverse displacements andelectrically connected thereto and a member supporting said positioningmember in engagement with said electrode member at a positionlongitudinally removed from said one position, said positioning memberelectrically insulating said electrode member from the last-namedsupporting member.

11. A discharge electrode tructure for an electrical precipitator as setforth in claim 10, wherein the positioning member is formed as a sleevesurrounding the electrode member.

FREDERICK W. PHILLIPS.

